<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#box {
	position: relative;
	width: 10px;
	height: 10px;
	margin: 200px auto;
	background: blue;
}
#box div {
	position: absolute;
	left: 50%;
	top: 50%;
	margin: -1px 0 0 -50px;
	width: 100px;
	height: 2px;
	background: red;
}
#box div:nth-of-type(1) {
	transform: rotate(0deg) translateY(87px);
}
#box div:nth-of-type(2) {
	transform: rotate(60deg) translateY(87px);
}
#box div:nth-of-type(3) {
	transform: rotate(120deg) translateY(87px);
}
#box div:nth-of-type(4) {
	transform: rotate(180deg) translateY(87px);
}
#box div:nth-of-type(5) {
	transform: rotate(240deg) translateY(87px);
}
#box div:nth-of-type(6) {
	transform: rotate(300deg) translateY(87px);
}
/*
	正N边形外角和 = 360
	正N边形外角 = 360/n
	正N边形内角 = 180 - 360/n

	正弦 Math.sin() 直角三角形中 对边和斜边的比值
	余弦 Math.cos() 直角三角形中 临边和斜边的比值 
	正切 Math.tan() 直角三角形中 对边和临边的比值 

	已知角度，和临边 求对边
	Math.tan(弧度)*临边 = 对边

	弧度 = 角度*Math.PI/180;

	对边 = Math.tan(角度*Math.PI/180)*临边 	
*/
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<script type="text/javascript">
	//console.log(Math.tan(60*Math.PI/180)*50); 87
</script>
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<body>
<div id="box">
	<div></div>
	<div></div>
	<div></div>
	<div></div>
	<div></div>
	<div></div>
</div>	
</body>
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